Bitumens used for road applications may have different origins. Venezuelan crude oils that naturally contain acidic molecules (naphthenic acids) are considered as having good qualities for manufacturing bitumen emulsions. Crude oils from other sources, e.g. Middle East oils, do not contain these acids. However, it is known to add (and incorporate) naphthenic acids to non-naphthenic bitumens in order to try to attain the quality of naphthenic bitumens. EP 416,682 discloses bitumen compositions comprising bitumen and at least one polymerized fatty acid contained in the bitumen and their use in bitumen emulsions for surface dressing applications suitable for roads.